It is known that certain veins in the human body contain valves, which largely function as one-way check valves to prevent blood from gathering or pooling in the lower extremities during the normal pumping action of the heart. That pumping action is characterized by alternate contractions and relaxations. During the contractions, blood in the circulatory system is advanced. Thus, as blood is pumped from the lower extremities back toward the heart, these venous valves function to prevent blood from receding due to gravitation during the relaxation phase.
Certain surgical procedures contemplate that a section of a patient's vein be substituted for a section of his artery, which may be deficient for one reason or another (e.g., an aneurysm, blockage, etc.). The use of the patient's own vein avoids problems of tissue-rejection, which often accompanies the use of foreign objects and substances (e.g., various metals or other materials, donor tissue, etc.). Moreover, the presence of foreign substances in the circulatory system may adversely effect the delicate balance of the patient's blood chemistry. However, to substitute a venous section for a corresponding arterial section, it is necessary to excise the venous valve(s) therefrom. At the same time, it would be desirable to minimize the damage to the endothelial tissue lining such vein.
To this end, several surgical techniques have been developed for excising the leaflets of the venous valve in preparation for such arterial substitution. According to one technique, a specially-configured hook-shaped catheter or probe, which somewhat resembles the "poker" of a set of fireplace tools, is provided. This catheter has a greatly-elongated rod-like portion, which is adapted to be inserted generally longitudinally into a vein. A fixed arm projects radially outwardly from the inserted marginal end portion of the probe, adjacent the tip. This arm is provided with a rearwardly-facing radially-extending sharpened cutting edge. Hence, the marginal end portion of the probe is pushed forwardly through the valve to be excised, and is then pulled rearwardly such that the sharpened cutting edge will engage and sever a proximate portion of a valve leaflet. However, upon information and belief, such "push through-and-pull back" manipulation of this probe must be repeated many times with this type of instrument to adequately excise a valve leaflet. Moreover, because of its "poker"-like configuration, the relatively-small inside diameter of the vein, and the fact that the surgeon is often precluded from having an unobstructed view of the inserted marginal end portion of the probe, the use of such probe is believed to unnecessarily damage the endothelial tissue during insertion, reciprocation when actually excising the valve, and subsequent withdrawal.
Other types of known prior art devices are shown in U.S. Pat. Nos. 4,601,706 (Aillon), 4,768,508 (Chin et al.), 4,739,760 (Chin et al.) and 4,722,258 (Marangoni et al.).